Chiral graphene nanoribbons: Objective molecular dynamics simulations and phase-transition modeling

Abstract

Edge-stress-induced spontaneous twisting of graphene nanoribbons Ramasubramaniam, A.; Koskinen, Pekka; Kit, Oleg; Shenoy, V.B. We present a continuum model for spontaneous twisting of graphene nanoribbons driven by compressive edge stresses. Based on a geometrically nonlinear theory of plates, we identify scaling laws for the dependence of twist angles on ribbon width. Strikingly, we find the existence of a critical width below which a ribbon will not undergo spontaneous twisting, preferring an in-plane stretching mode instead. The model predictions are shown to be in excellent qualitative and quantitative agreement with density-functional tight-binding simulations. More generally, our model provides a unifying picture of twisting in graphene nanoribbons with different edge orientations and chemical functionalizations that have been reported recently in the literature. V C 2012 American Institute of Physics. [http://dx.

Quantum effects in graphene monolayers: Path-integral simulations

“…Thus, there has been recently a rise of interest on thermodynamic properties of graphene, both theoretically and experimentally. [17][18][19][20] Finite-temperature properties of graphene have been studied by molecular dynamics and Monte Carlo simulations using ab-initio, [21][22][23] tight binding, [24][25][26][27] and empirical interatomic potentials. 5,[28][29][30][31][32] In most applications of these methods, atomic nuclei were described as classical particles.…”

Formation of Helices in Graphene Nanoribbons under Torsion

“…20 This is important as edge chemistry alone can induce extended deformations in GNRs. 7,16 We also note that a large amount of simulations is required to understand the helix formation. SCC-DFTB is appropriate for conducting this investigation as its offers both compu-tational efficiency and accuracy for geometries, even for biological systems which contain many atomic species.…”

“…The method has been used to model a number of tubular 23,24 and graphene structures [24][25][26] including twisted GNRs. [7][8][9]16,27 The recent inclusion of the SCC correction 18 with a helical Ewald sum 28 improves the description of heteronuclear interactions by considering electron transfer, such as from the C to the F edge atoms. 20 This is important as edge chemistry alone can induce extended deformations in GNRs.…”

Multiscale real-space quantum-mechanical tight-binding calculations of electronic structure in crystals with defects using perfectly matched layers

“…The position of each carbon atom in the graphene sheet is given by starting at one of the two atoms in the unit cell and adding an integer linear combination of a 1 and a 2 : Knowing the lattice vectors a 1 and a 2 and the positions of the two carbon atoms labeled by 1 and 2, X n , we can construct the whole 2D Graphene layer as [AD12]:…”